Transition from Anisotropic to Isotropic Crystal Growth Enables Ultrahigh-Rate Zn Metal Anodes in Batteries
Year: 2026
Type: preprint
Abstract: Achieving controllable crystallization under dynamic, far-from-equilibrium conditions remains a fundamental challenge underlying many technologically important processes, including highpower batteries based on metal anodes. Recent studies have identified crystal anisotropy as a key factor governing electrodeposit morphology. Departing from conventional wisdom, we find that suppressing highly anisotropic facet-dependent growth by slowing interfacial kinetics results in more isotropic, morphologically uniform electrodeposition. Taking Zn as an example, we use a nonaqueous Zn(Otf)2 in acetonitrile electrolyte to promote the formation of dense irregular-shaped nuclei in sharp contrast to the faceted nuclei formed in conventional aqueous Zn(Otf)2 and ZnSO4 electrolytes. 3-D profilometry shows the isotropic growth of Zn in the organic electrolyte leads to significantly flatter deposit morphology compared to the aqueous electrolytes. We rigorously characterize the electrochemical properties of the Zn(Otf)2 in acetonitrile electrolyte and compare it to aqueous Zn(Otf)2 and ZnSO4 electrolytes, using a combination of ultra-fast scan cyclic voltammetry on an ultra-microelectrode (UME) and interfacial molecular dynamics simulations. Our measurements show the plating/stripping kinetics in the organic electrolyte are reduced by over 100-fold relative to the aqueous electrolytes, while the transport properties are only slowed by 3 to 4-fold. Using a two-step Butler-Volmer model, we find slow interfacial kinetics in the organic electrolyte eliminate the facet-dependent rate-determining step present in aqueous electrolytes, directly linking sluggish kinetics to isotropic growth. The uniform morphology and the suppression of Zn corrosion reactions in the organic electrolyte lead to over a 10-fold improvement in cycling stability over benchmark aqueous Zn electrolytes, both at moderate current densities (1 mA/cm2) and ultra-fast current densities (200 mA/cm2). Taken together, these results highlight the viability of using a fully organic Zn electrolyte for Zn batteries and Zn electroplating systems, challenging the prevailing assumption that organic electrolytes are inferior under fast cycling conditions. Moreover, the demonstrated correlation between interfacial kinetics and electrodeposit morphology offers a generalized framework for morphological control in metal deposition.
Source: ChemRxiv
Institutions: The University of Texas at Austin, Texas Materials Institute
Language: English
Topic: Aqueous and Flow Batteries
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220859051